The present disclosure generally relates to tagged scale inhibition compositions and methods of inhibiting scale. More particularly, the present invention relates to imidazole tagged scale polymeric inhibitors for use in water treatment and/or oil field applications.
Scale inhibiting polymers are often used in water treatment and oil field applications to minimize and/or prevent scale deposition. The deposition of scale can occur in the transport of aqueous mixtures and in subterranean rock formations due to the presence of water bearing alkaline earth metal cations such as calcium, barium, strontium, and the like as well as the presence of anions such as phosphate, sulfates, carbonates, silicates and the like. When these ions are in sufficient concentrations, a precipitate can form that builds up on interior surfaces of the conduits used for transport or in the subterranean rock formations, which restrict flow of the media of interest, e.g., water or oil. In oilfield applications, scales that are commonly formed include calcium sulfate, barium sulfate, and/or calcium carbonate that are generally formed in the fresh waters or brines used in well stimulation and the like as a result of increased concentrations of these particular ions, the water pH, pressures, and temperatures. In addition, calcium phosphate can form from the phosphate chemistry that is commonly used to treat wells and pipes for corrosion. The buildup of these mineral precipitates can reduce or block flow in the conduits and rock formations as well as cause other problems. In many cases, the first warning of the existence of a significant scale deposit may be a decline in well performance. In these instances, scale removal techniques may become necessary. As a result, a potentially substantial cost including downtime is required lost to effect repair as a result of scaling.
Scale inhibiting materials are often added directly to a fluid to be treated or applied to oil bearing rock formations by means of “squeeze treatment”. Squeeze treatment is a treatment used to control or prevent scale deposition in a rock formation. In the squeeze application, the scale inhibitor is pumped into a water-producing zone and attaches to the formation by chemical adsorption or by temperature-activated precipitation. When the well is put back into production, the scale inhibitor leaches out of the formation rock to treat the fluid. Some chemicals typically used in scale-inhibitor squeeze applications include phosphonated carboxylic acids or polymers.
Scale formation is only controlled if the scale inhibitor polymer is present at a treatment level equal to or above the product's defined minimum inhibitor concentration. When the scale inhibitor is below the minimum inhibitor concentration such as may occur during use, adsorption or degradation, additional amounts are then needed. For example, once the well is subjected to the squeeze application and the well is again operational, the concentration of the scale inhibitor in the produced fluids will diminish over time until such time that the scale inhibitor is at about or below the minimum inhibitor concentration. However, it is difficult to determine when more scale inhibitor is needed and in which conduit or well it is needed. To address this problem, scale inhibitors are often tagged or labeled so that the presence or absence of the scale inhibitor can be readily detected. Prior art scale inhibitors are generally tagged by introduction of specific atoms such as phosphorous, boron, and the like such that the concentration can be readily detected by inductively coupled plasma (ICP) analysis for the tagged atom. Alternatively, the scale inhibitor can be tagged fluorescent moieties. However these compounds are generally limited to structures that include one or more conjugated six member benzene rings that fluoresce at about 292 nm.
While the prior art fluorescent tagged scale inhibitors are suitable for their intended, there is a need in the art for additional fluorescent moieties that emit at different wavelengths, which would be beneficial in multi-tagged systems where multiple scale inhibitors with tags having different fluorescent wavelengths are utilized. Examples of such a system would be when more than one wells are drilled and the oil is collected from one central location. The multi-tagged system would allow the operators to know which specific wall requires more antiscalent, simply by looking at what frequency is missing.